1. Field of the Invention
The present invention relates to a turbomachinery such as a high temperature pump for pumping a high temperature liquid.
2. Description of the Related Art
In a type of a conventional motor pump for pumping a high temperature liquid, an axial flow impeller called an "inducer" is provided at a position upstream of a main centrifugal impeller. The inducer has a cylindrical body and vanes spirally provided on an outer surface of the cylindrical body, and is usually made of ceramics because of manufacturing convenience and good heat resisting properties.
The inducer is attached to the tip end of a metallic pump shaft in the motor pump in a following manner, for example. First, both ends of the inducer and the shaft are formed with radial mutually engageable grooves, then they are abutted to each other and fixed to each other by a fastening means such as bolts.
However, in a high temperature motor pump, the inducer is subjected to a temperature variance because it is heated by a high temperature liquid when it is operated to handle it and is cooled to a room temperature when it is not operated. As a result, the attachment of the inducer to the pump shaft may be loosened due to a difference between the expansion coefficients of the different materials, which may cause misalignment of the axes of the inducer and the motor shaft resulting in unfavorable operating conditions. Also, the conventional method requires much work for forming the engagement grooves both in the inducer and the motor shaft, leading to a high manufacturing cost.